Salmonella Rissen

Background: Salmonella enterica subsp. enterica serovar Rissen (antigenic formula 6,7,14:f,g:-) is a serovar of the O:7 (C1) serogroup. This serovar was first nomenclating by Rohde & Tiedje during early 1960s. In Japan, Kaneko reported the first isolate of S. Rissen from patients with sporadic diarrhea was found during the period from April 1985 to December 1994 in Yamanashi Prefecture. Recently, serovar Rissen is the 4th most common nontyphoidal Salmonella serovar isolated from human infections in Thailand.

NCBI PD link for serovar Rissen: https://www.ncbi.nlm.nih.gov/pathogens/isolates/#taxgroup_name:(%22Salmonella%20enterica%22)%20AND%20computed_types:(%22serotype=Rissen%22)

Genetic characteristics: Serovar Rissen has been found to be polyphyletic with three lineages identified and one stand-alone singleton that does not cluster with any other Salmonella Rissen isolates. Serovar Rissen ST469 has been found worldwide, in countries such as Thailand, China, and Italy. This sequence type is the most common ST for serovar Rissen. ST8877 has been isolated from a cracked table egg in Sudan.

Pornsukarom et al. reported that all Thai Rissen isolates in their study were multidrug-resistant and more than 90% were resistant to ampicillin, sulfisoxazole, tetracycline and streptomycin. Conversely, half of the Salmonella Rissen isolates in the USA were pan-sensitive while some were resistant to only tetracycline. Wang et al. observed that Salmonella Rissen human isolates (anal swabs or feces) had the common resistance profile: ampicillin, trimethoprim-sulfamethoxazole, and tetracycline; resistance were conferred by bla_TEM, tetA, and sul3, respectively. A study from India reported on multidrug-resistant Salmonella Rissen strains (resistant to nalidixic acid, sulfamethizole, and carbanicillin) isolated from seafood in Cochin, India. Moreover, Spanish Salmonella Rissen isolated from live mussels carried mcr-1 gene and other antimicrobial resistance genes (aac(6')-Iaa, aadA1, aadA2, bla_TEM-1B, cmlA1, sul1, sul3, tet(A), and dfrA1).

Animal reservoir: Swine is the major animal reservoir of serovar Rissen, including the pork production chain. However, Salmonella Rissen can be also detected in seafoods.

Geographical distribution: Serotype Rissen has been reported especially in Asian countries such as Thailand, Vietnam, China, Japan, and India, but it has also been found in Italy, France, Spain.

Human outbreaks: Two outbreaks linked to Salmonella Rissen have been associated with food. Some examples are shown below.

Year	Location	Associated source	Number of cases
2020	France	Fuet from Spain	18
2008-2009	US: multistate	White pepper	87

Border rejections: Multiple border rejections associated with serovar Rissen have been reported. Here we selected five as examples.

Year	Exporting country	Importing country	Associated source	Product category
2024	Denmark	Finland	Rapeseed expellers	Feed materials
2022	Spain	Belgium	Turkey processed animal protein¹	Feed materials
2022	Ukraine	Germany	Sunflower cake	Feed materials
2020	Spain	Switzerland	Chorizo sausage	Meat and meat products (other than poultry)
2020	Belgium	Austria	Dog feed²	Pet food

¹ Salmonella Rissen and Muenster were found.

² Salmonella Rissen and monophasic Typhimurium were found.

Recalls:

Year	Location	Recalled food	Type
2020	France	Fuet¹	Food
2019	US: multistate	Pig ears²	Pet treats

¹ This recall was caused by France to withdraw all fuet with all dates and bearing the mark ES-10.12147/B-CE carried out in various stores across France.

² This recall was caused by a multistate human outbreak linked to several Salmonella serovars, including Rissen, linked to pig ears treats for dogs.

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Salmonella Rissen